System and method for bonding package lid

ABSTRACT

Disclosed herein is a device having a shaped seal ring comprising a workpiece, the workpiece comprising at least one dielectric layer disposed on a first side of a substrate, a seal ring disposed in the at least one dielectric layer, and at least one groove in the seal ring. A lid is disposed over the workpiece, the workpiece extending into a recess in the lid and a first thermal interface material (TIM) contacts the seal ring and the lid, with the first TIM extending into the at least one groove. The workpiece is mounted to the package carrier. A die is mounted over a first side of workpiece and disposed in the recess. A first underfill a disposed under the die and a second underfill is disposed between the workpiece and the package carrier. The first TIM is disposed between the first underfill and the second underfill.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is a divisional of and claims priority to U.S. patentapplication Ser. No. 14/163,000, filed on Jan. 24, 2014, entitled“System and Method for Bonding Package Lid,” which application is herebyincorporated herein by reference in its entirety.

BACKGROUND

Semiconductor devices are used in a variety of electronic applications,such as, for example, personal computers, cell phones, digital cameras,and other electronic equipment. Semiconductor devices are typicallyfabricated by sequentially depositing insulating or dielectric layers,conductive layers, and semiconductor layers of material over asemiconductor substrate, and patterning the various material layersusing lithography to form circuit components and elements thereon.

The semiconductor industry continues to improve the integration densityof various electronic components (e.g., transistors, diodes, resistors,capacitors, etc.) by continual reductions in minimum feature size, whichallow more components to be integrated into a given area. In somedevice, multiple dies are stacked vertically to reduce the footprint ofa device package and permit dies with different processing technologiesto be interconnected. As the sizes of active devices on a die shrink,the heat dissipation for the increasingly compact active devices ismanaged by attaching a lid over the stacked dies. The lid protects thedies and provides a path to conduct heat away from the dies.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIGS. 1 through 10 illustrate cross-sectional views of intermediatesteps in forming a workpiece having a shaped seal ring according to anembodiment;

FIGS. 11A through 11C illustrate cross-sectional views of devices withvarious embodiments of shaped seal rings and lids; and

FIG. 12 is a flow diagram illustrating a method of forming a workpiecewith a shaped seal ring according to an embodiment.

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated. The figures aredrawn to illustrate the relevant aspects of the embodiments and are notnecessarily drawn to scale.

DETAILED DESCRIPTION

The making and using of the presented embodiments are discussed indetail below. It should be appreciated, however, that the presentdisclosure provides many applicable concepts that can be embodied in awide variety of specific contexts. The specific embodiments discussedare merely illustrative of specific ways to make and use the describeddevice with a shaped seal ring and bonded lid, and do not limit thescope of the disclosure.

Embodiments will be described with respect to a specific context, namelymaking and using shaped seal rings useful in, for example, bonding lids,heat sinks covers, casing or the like to wafers, dies, substrates orother structures. Other embodiments may also be applied, however, to thebonding of substrates, packages, structures or devices or combinationsof any type of integrated circuit device or component.

The embodiments of the present disclosure are described with referenceto FIGS. 1 through 12, and variations of the embodiments are alsodiscussed. Throughout the various views and illustrative embodiments ofthe present disclosure, like reference numbers are used to designatelike elements. Additionally, the drawings are intended to beillustrative, are not to scale and not intended to be limiting. Notethat, for simplification, not all element numbers are included in eachsubsequent drawing. Rather, the element numbers most pertinent to thedescription of each drawing are included in each of the drawings.

Three dimensional integrated circuit (3D IC) packages are commonlyformed by attaching one or more top dies to carrier dies, which are inturn attached to a package substrate. These dies and substrate areattached by way of, for example, ball grid arrays (BGAs), land gridarrays (LGAs), solder balls, studs, wire bonds, or other conductiveconnectors. One or more of the dies may be formed with a seal ring in aredistribution layer (RDL) around the outside edge of the die. The sealring may be formed of metal elements extending through the dielectriclayers of the RDL. The seal ring prevents the dielectric layers frompeeling, particularly when the die is sawn from the wafer.

In order to ensure that the stacked dies remain connected and theconductive connections between the dies remain intact an underfill isapplied between each the dies. Disclosed herein is a method for shapingthe top surface of the seal ring so that a lid acting as a heat sink maybe applied over the dies with a thermal interface material (TIM) betweenthe seal ring and the lid. It has been discovered that a grooved orshaped seal ring surface provides an improved bonding surface for theTIM that prevents underfill material on each side of the TIM fromseeping between the TIM and the seal ring, weakening the bond andreducing the thermal interface between the seal ring and TIM.

FIG. 1 is a cross-sectional view illustrating an intermediate step information of a workpiece 100 according to an embodiment. A workpiece 100comprises a substrate 102 having one or more devices, vias 116 orstructures formed therein. An RDL 104 with one or more dielectric layersis formed on the first side of the substrate 102, with one or moreconductive features 114 disposed in the dielectric layers. Lands 118 areformed on the RDL 104, with the conductive features 114 connecting thelands 118 to the vias 116, devices or structures of the substrate 102.In an embodiment, a passivation layer 106 and a protective layer 108 areformed over the RDL 104, with openings exposing the lands 118. Underbump metal layers (UBMs) 110 are formed in the openings of thepassivation layer 106 and the protective layer 108, and one or moreconnectors 112 are applied over the UBMs 110.

In an embodiment, the substrate 102 is a semiconductor, a polymer, aninsulator, or the like. In some embodiments, the substrate 102 is aportion of a semiconductor wafer, and one or more active devices, suchtransistors, diodes, photosensors, or the like are formed in the bodyof, or on the surface of, the substrate 102. In other embodiments, thesubstrate 102 is an interposer, carrier or supporting structure madefrom, for example, a polymer, glass, or another insulating material.

In an embodiment, one or more conductive features are formed in or onthe surface of the substrate 102. In an embodiment, conductivestructures such as vias 116 are formed in the substrate 102. Here, thedrawings illustrate vias 116 in the substrate 102 for simplicity.However, the drawings are intended to be exemplary and not limiting, asany combination of active devices, traces, passive devices, or one ormore other structures may be disposed in or on the substrate 102.

The RDL 104 is formed with one or more metal layers and one or moreintermetal dielectric layers (IMDs). The IMDs are disposed between themetal layers. The IMDs have conductive features 114 such as viasdisposed in a dielectric connecting to conductive features 114 such astraces in the dielectric of the metal layers. In an embodiment, thedielectric material of the metal layers and IMDs is, for example, asilicon oxide, nitride, carbide, polymer, or another insulating ordielectric material, and may be formed using a chemical vapor deposition(CVD), spin-on or other deposition process. The conductive features 114may be formed using a damascene or dual damascene process, with openingsetched in the dielectric layer of the RDL 104, and a conductive materialsuch as copper, aluminum, or the like deposited in the opening and thenplanarized. The RDL 104 is built up by forming multiple metal layers andIMDs, with the traces and vias routing electrical connections fromstructures on the substrate 102 to the top surface of the RDL 104.

Lands 118 are formed on top surface of the RDL 104 or are formed in thetop layer of the RDL 104 as part of the RDL formation process. The lands118 are configured to accept UBM structures or to accept directapplication of a connector 112. In an embodiment, the lands 118 areformed from, for example, copper, aluminum, or another metal orconductive material.

The passivation layer 106 and protective layer 108 are formed over atleast a portion of the lands 118 and over the top surface of the RDL104. In an embodiment, the passivation layer 106 is formed from, forexample, a nitride, an oxide, an oxynitride, a carbide such as siliconcarbide, or another material, formed through a deposition, masking andetching process, or through a masking and deposition process. Theprotective layer 108 is from from a polymer such as polybenzoxazole(PBO), or an epoxy, polyimide or other material, which is applied overthe passivation layer 106.

One or more UBMs 110 are formed in the openings in the protective layer108 and passivation layer 106 with a process such as deposition, maskingand etching. In an embodiment, the deposition process is CVD,sputtering, or the like, and the UBM material is a metal such as copper,nickel, titanium or the like. One or more connectors 112 are formed overthe lands 118. In an embodiment, the connectors 112 are solder balls orconnective bumps disposed on the UBMs 110. In another embodiment, theconnectors 112 are studs, pins, wires or another structure formed on theland 118 with the UBMs 110 omitted.

FIG. 2 is a cross-sectional view illustrating thinning of the backsideof the substrate 102 according to an embodiment. The workpiece 100 isinverted to access the backside of the substrate 102. In an embodiment,the workpiece 100 is attached at the first side to a carrier (omittedfor clarity) with an adhesive or the like. The carrier may be a supportor other structure permitting handling and processing of the workpiece100 in subsequent steps.

The backside of the substrate 102 is prepared for processing afterbonding the workpiece 100 to the carrier, where used. In an embodiment,vias 116 formed in the substrate 102 are exposed by grinding orotherwise reducing the backside of the substrate 102. In anotherembodiment, the backside of the substrate 102 is planarized, cleaned orotherwise processed.

FIG. 3 is a cross-sectional view illustrating formation of a seal ring304 on the workpiece 100 according to an embodiment. An RDL 302 isformed on the backside of the substrate 102 with formation processessuch as those for the RDL 104 as described above for FIG. 1. The RDL 302has a seal ring 304 formed therein bordering the outside edge of theworkpiece 100. In an embodiment, the seal ring 304 is formed from metalelements created when the conductive elements 306 are formed in eachdielectric layer of the RDL 302. In such an embodiment, the seal ring304 may be build up from multiple stacked metal elements. For example,the conductive elements 306 and seal ring 304 elements may be formedfrom copper in dielectric layers made from silicon oxide, siliconnitride, silicon carbide or other dielectric material. In such anexample, openings for the seal ring 304 may be formed in each dielectriclayer, and the seal ring 304 elements are formed in the same processstep as the conductive elements 306.

In another embodiment, the seal ring 304 may be formed after theconductive elements 306 are formed or after the RDL 302 itself isformed. In such an embodiment, the seal ring 304 may be formed from oneor more metal layers that are formed in a channel etched in the RDL 302after all of the dielectric layers are formed. Alternatively, the sealring 304 may be formed from metal elements that are formed as eachdielectric layer is formed, but in a process step separate from formingthe conductive elements 306. In an embodiment, the seal ring 304 extendsfrom the top surface of the RDL 302 to the substrate 102. In otherembodiments, the seal ring 304 stops in the RDL 302 before the substrate102, with at least a portion of the dielectric disposed between thesubstrate 102 and the seal ring 304.

FIG. 4 is a cross-sectional view illustrating formation of a protectivelayer 404 and UBMs 406 on the workpiece 100 according to an embodiment.Lands 408 are formed on the RDL 302 and connected to the conductiveelements 306. A passivation layer 402 and protective layer 404 areformed on the RDL 302, with openings exposing the lands 408. In anembodiment, UBMs 406 are formed over the lands 408 in the openings inthe passivation layer 402 and the protective layer 404. The lands 408,passivation layer 402, protective layer 404 and UBMs 406 are formedaccording to the processes described above with respect to FIG. 1.

The passivation layer 402 and protective layer 404 are illustrated hereas stopping between the lands 408 and the seal ring 304. However, thisarrangement is merely exemplary and is not intended to be limiting. Inan embodiment, the passivation layer 402 and the protective layer 404may be formed by masking and deposition, or formed from a photosensitivematerial that is exposed with a pattern, developed and partly strippedto expose the seal ring 304 or to expose both the seal ring 304 and aportion of the RDL 302 surface. In other embodiments, the seal ring 304extends above the surface of the RDL 302 and the passivation layer 402and/or protective layer 404 are formed around the seal ring 304. Inother embodiments, the passivation layer 402 and/or protective layer 404are patterned with an opening over the seal ring 304. In such anembodiment, a metal feature is formed in the opening to extend theheight of the seal ring 304 to at least the top surface of thenpassivation layer 402 or the protective layer 404.

FIG. 5 is a cross-sectional view illustrating masking and shaping of theseal ring 304 according to an embodiment. A mask 502 is formed andpatterned over the seal ring 304, and the seal ring 304 is etching usingthe mask 502. In an embodiment, the mask 502 is a photoresist that isspun on, and then patterned and developed to leave openings in the mask502 over the seal ring 304. The seal ring 304 is etched to creategrooves 602 (See, e.g. FIG. 6) in the seal ring 304 according to thepattern of the mask 502. For example, where the seal ring 304 is copperthe seal ring 304 is wet etched using an acid such as phosphoric acid,nitric acid, hydrochloric acid, or with another etchant. Where the sealring, is, for example, aluminum, the seal ring 304 may be wet etchedusing phosphoric acid, hydrochloric acid, hydrofluoric acid or anotheretchant, or the seal ring 304 may be plasma etched with phosphoric acid,acetic acid nitric acid, a combination of the same or another etchant.

FIG. 6 is a cross-sectional view illustrating the shaped or etched sealring 304 with grooves 602 according to an embodiment. In an embodiment,the seal ring 304 is anisotropically etched, resulting in grooves 602with substantially square bottoms. In other embodiment, the grooves arecreated with a subtractive process such as ion milling or with anadditive process such as, for example, forming ridges defining thegrooves 602 by depositing material over a patterned mask and thenremoving the mask. In an embodiment, the grooves 602 are substantiallyconcentric with each other and border the workpiece 100 in the seal ring304.

It has been discovered that formation of grooves 602 in the seal ring304 and bordering the workpiece 100 creates an improved seal when athermal interface material (TIM) is applied over the grooves 602 of theseal ring 304. The grooves 602 in the seal ring 304 increase the surfacearea of the region where the TIM contacts the seal ring 304 and preventsunderfill inside or outside the seal ring 304 from flowing between theTIM and the seal ring 304 during subsequent processing and use. In anembodiment, 1 or more grooves 602 are formed in the seal ring 304.Additionally, 2 to 8 grooves 602 in the seal ring 304 have beendiscovered to be critical to providing advantageous clamping and sealingof the TIM to the seal ring 304. A width between about 2 μm and about 30μm and a depth of between about 1 μm and about 50 μm for each of thegrooves 602 is critical to provide advantageous joining of the grooves602 and seal ring 304 to the TIM.

FIG. 7 is a cross-sectional view illustrating mounting a die 704 on theworkpiece 100 and mounting the workpiece 100 on a package carrier 702according to an embodiment. A die 704 is attached to the UBMs 406 andelectrically connected to the lands 408 by way of connectors 604 such assolder balls, studs, bumps or the like. In some embodiments the die 704is a package, substrate, board, carrier, multiple dies, or anotherstructure. Where the workpiece 100 is part of a larger group ofworkpieces, such as on a wafer, the workpiece 100 is be cut or diced tosingulate the workpiece.

The workpiece 100 is also mounted to a package carrier 702 by attachingthe connectors 112 to the package carrier 702. The package carrier 702may comprise at least a package substrate 708 and package connectors 706disposed on the opposite side of the package carrier 702 from theworkpiece 100. In an embodiment, the package substrate 708 has one ormore interconnections disposed therein permitting the die 704 and/or theworkpiece 100 to be in electrical signal communication with the packageconnectors 706. The package connectors 706 are configured to permitmounting of the completed device on another board, die, substratecarrier or package.

In an embodiment, the workpiece 100 is, for example, a processor, andthe die 704 is one or more memory dies. In such an embodiment, theworkpiece 100 may be in signal communication with the die 704 so thatthe workpiece 100 may fetch data or instructions from the die 704. Thepackage carrier 702 may be a carrier having a layout or pitch of packageconnectors 706 different from the layout or pitch of the connectors 112,with the package carrier 702 connecting the processor of the workpiece100 for communication with a PCB (not shown). In other embodiments, thedie 704 is, for example, a dedicated signal processing or videoprocessing die, while the workpiece 100 is a general processor thatoffloads a portion of processing load to the die 704. It should beunderstood that the foregoing examples are not intended to be limiting,and that the die 704 and workpiece 100 may each be any type of die,chip, memory, processor, package or other device.

FIG. 8 is a cross-sectional view illustrating applying package underfill802 and workpiece underfill 804 according to an embodiment. The packageunderfill 802 is applied between the die 704 and the workpiece 100, andthe workpiece underfill 804 is applied between the workpiece 100 and thepackage carrier 702. In an embodiment the package underfill 802 andworkpiece underfill 804 are form from, for example, an epoxy, apolyimide, a polymer, or another insulating material. The packageunderfill 802 and workpiece underfill 804 are applied as a gel or liquidand may be forced into the spaces around the respective connectors 604and 112, and then subsequently cured. In an embodiment, the packageunderfill 802 and workpiece underfill 807 avoids the grooves 602 of theseal ring 304 to prevent the underfills 802 and 804 from interferingwith TIM application (See, e.g., FIG. 9).

FIG. 9 is a cross-sectional view illustrating applying thermal interfacematerials (TIMs) 902 and 904 according to an embodiment. A package TIM902 and workpiece TIM 904 are applied to the die 704 and seal ring 304,respectively. An adhesive 906 is also applied to the package carrier702. The TIMs 902 and 904 are structures that fill air gaps orimperfections in surfaces to provide a thermal sink for heat generatedby those surfaces. In the illustrated embodiment, package TIM 902 isapplied to the top surface of the die 704 and permits the transmissionof heat from the die 704. The workpiece TIM 904 is applied to the sealring 304 and permits transmission of heat from the workpiece 100.

In an embodiment, the TIMs 902 and 904 are thermally conductive gels,pastes, pads, greases, or phase change materials with the greatestpossible thermal conductivity, typically between about 0.5 W/(m·K) andabout 10 W/(m·K). For example, a thermal grease may be a ceramic ormetal, such as beryllium oxide, aluminum nitride, aluminum oxide, zincoxide, silver, aluminum, or the like, suspended in a silicone-based gel.In other examples, TIMS 902 and 904 may be a liquid metal paste ofgallium alloys, or a metal alloy pad that is reflowed to adhere the TIMmaterial to a surface.

FIG. 10 is a cross-sectional view illustrating applying a lid 1002according to an embodiment. The workpiece 100 and die 704 fit within arecess of the lid 1002. The lid 1002 is adhered to the package carrier702 by the adhesive 906. The TIMs 902 and 904 provide additionaladhesion for the lid 1002. The lid 1002 is a structure that acts, in anembodiment, as a heat sink, with the interior surface of the lid 1002contacting the package TIM 902 and workpiece TIM 904. After applicationof the lid 1002, the workpiece TIM 904 substantially fills the grooves602 under the workpiece TIM 904, providing a thermal interface betweenthe seal ring 304 and the lid 1002.

It has been found that the grooves 602 filled with workpiece TIM 904enhance clamping force between the lid 1002 and workpiece 100 andprevents delamination of the lid 1002 from the workpiece 100.Additionally, after application of the lid 1002, the grooves 602 andworkpiece TIM 904 prevent bleeding of the package underfill 802 betweenthe lid 1002 and seal ring 304 from slumping or migration due toprocessing, vibration, high temperatures or other adverse conditions.The grooves 602 and workpiece TIM 904 also prevent the workpieceunderfill 804 from creeping over the top surface of the workpiece 100and infiltrating between the lid 1002 and seal ring 304.

In an embodiment, the lid 1002 is a heat conductive material such asaluminum, copper, or the like. Heat from the die 704 and workpiece 100is transferred to the lid by way of the TIMs 902 and 904. The lid 1002dissipates the heat of the die 704 and the workpiece 100, permittingthose devices to operate at higher speeds and with less thermal stress.In the illustrated embodiment, the workpiece TIM 904 is applied to covera portion of the seal ring 304, leaving one or more grooves 602 lessthan completely filled. However, at least one of the grooves 602 isfilled with the workpiece TIM 904.

FIG. 11A illustrates an alternative embodiment of the workpiece TIM 904as applied to the seal ring 304. In such an embodiment, the workpieceTIM 904 may completely cover, or substantially cover, all of the sealring 304, substantially filling all of the grooves 602. FIG. 11A alsoshows the workpiece TIM 904 preventing the package underfill 802 andworkpiece underfill 804 from infiltrating between the seal ring 304 andlid 1002. In such an embodiment, the workpiece TIM 904 separates thepackage underfill 802 and workpiece underfill 804 on the surface of theworkpiece 100.

FIG. 11B illustrates an alternative embodiment of the lid 1002 interfacewith the workpiece TIM 904. In an embodiment, the bond between the lid1002 and the workpiece TIM 904 is enhanced by ridges 1102 in the lid.The ridges 1102 may be milled or formed on the interior surface of thelid 1002, and may extend into the workpiece TIM 904 so that theworkpiece TIM 904 fills the grooves between the ridges 1102. In anembodiment, ridges 1102 may complement the grooves 602 in the seal ring304, with one ridge 1102 substantially aligned with, and sized similarlyto, a respective groove 602. In an embodiment, the lid 1002 has a numberof ridges 1102 matching the number of grooves 602 in the seal ring 304,and in other embodiments, the lid 1002 may have the same number, ormore, ridges 1102 than the number of grooves 602 in the seal ring 304.While the ridges 1102 of the lid 1002 are illustrated here assubstantially “U” shaped or rectangular, it should be recognized thatsuch shape is merely illustrative and not limiting, and that the ridges1102 may have other shapes.

FIG. 11c illustrates an alternative embodiment of the lid 1002 interfacewith the workpiece TIM 904. The lid 1002 may be formed with “V” shaped,or triangular ridge 1104.

FIG. 12 is a flow diagram illustrating a method 1200 of forming aworkpiece with a shaped seal ring according to an embodiment. Theworkpiece comprising a die, wafer, substrate or other structure isformed in block 1202. A passivation layer and/or RDL is formed on afirst side of the workpiece in block 1204, and UBMs and connectors areformed over the RDL on the first side of the workpiece in block 1206.The workpiece is flipped in block 1208, optionally bonded to a carrierin block 1210, and vias or other conductive structures in the substrateare optionally exposed at the second side of the workpiece in block1212. A second RDL, including the seal ring, is formed on the secondside of the workpiece in block 1214, and UBMs are formed over the secondRDL in block 1216. The seal ring is masked and etched, or otherwiseshaped, in block 1218. A package is mounted on the second side of theworkpiece in block 1222 and the workpiece is mounted to the packagecarrier in block 1224. Underfill is applied between the package andworkpiece and between the workpiece and package carrier in block 1224.An adhesive is applied to the package carrier and a lid is attached inblock 1226.

Thus, according to an embodiment, a device having a shaped seal ringcomprises a workpiece, the workpiece comprising at least one dielectriclayer disposed on a first side of a substrate, a seal ring disposed inthe at least one dielectric layer, and at least one groove in the sealring. A lid is disposed over the workpiece, the workpiece extending intoa recess disposed in the lid and a first thermal interface material(TIM) contacts the seal ring and a first surface of the recess in thelid, with the first TIM extending into the at least one groove. The lidcomprises one or more ridges disposed in the recess and contacting thefirst TIM. The workpiece is mounted to the package carrier. A die ismounted over a first side of workpiece and disposed in the recess. Afirst underfill is disposed under the die and a second underfill isdisposed between the workpiece and the package carrier. The first TIM isdisposed between the first underfill and the second underfill.

A device according to another embodiment comprises a workpiece having aseal ring disposed in a first side and bordering the workpiece, whereinthe seal ring has at least one groove disposed in a top surface, a liddisposed over the workpiece and having a recess in a first side, theworkpiece extending into the recess and a first TIM disposed on the sealring and extending into the at least one groove, the first TIMcontacting a first surface of the recess in the lid. The seal ring hasbetween about 4 and about 6 grooves. Each of the grooves has widthbetween about 2 μm and about 30 μm and a depth of between about 1 μm andabout 50 μm. The lid comprises one or more ridges disposed in therecess, the one or more ridges contacting the first TIM. The one or moreridges in the lid have a rectangular shape or a triangular shape. Theridges complement the grooves. A die is mounted over the first side ofthe workpiece by one or more connectors, the die in signal communicationwith the workpiece. A second TIM contacts a second surface of the recessin the lid and also contacts the die. The device further comprises apackage carrier, and the workpiece is mounted to the package carrier byone or more connectors. An adhesive is disposed on a first surface ofthe package carrier, the adhesive adhering the lid to the packagecarrier. A first underfill is disposed between the die and theworkpiece, and a second underfill disposed between the workpiece and thepackage carrier. The first TIM is disposed between the first underfilland the second underfill.

A method of forming a device according to an embodiment comprisesforming a seal ring on a first side of a workpiece, forming at least onegroove in the seal ring and bordering the workpiece, applying a firstthermal interface material (TIM) to the seal ring and attaching a lidover the workpiece. The lid has a recess in a first side, the lidcovering the workpiece with the workpiece extending into the recess, anda surface of the recess contacting the first TIM. After the attachingthe lid, the first thermal interface material extends into the at leastone groove. The method further comprises mounting a die over the firstside of workpiece, the die in signal communication with the workpieceafter the mounting the die, applying a first underfill between the dieand the workpiece, and applying a second TIM to the die, the surface ofthe recess in the lid contacting the second TIM after the attaching thelid. The method also further comprises mounting the workpiece to apackage carrier, applying a second underfill between the workpiece andthe package carrier, and applying an adhesive to the package carrier.The attaching the lid comprises attaching a surface of the lid to theadhesive and the first TIM is disposed between the first underfill andthe second underfill on the outside surface of the workpiece.

In an embodiment, a method includes forming a seal ring on a first sideof a workpiece. At least one groove is formed in the seal ring. A firstthermal interface material (TIM) is applied to the seal ring. A lid isattached over the workpiece. A first side of the lid has a recess. Thelid covers the workpiece with the workpiece extending into the recess. Asurface of the recess contacts the first TIM. The first TIM extends intothe at least one groove after the lid is attached over the workpiece.

In another embodiment, a method includes forming a dielectric layer overa substrate. A recess is formed in the dielectric layer. The recess isfilled with a conductive material to form a seal ring within thedielectric layer. The seal ring is patterned to form one or more groovesin the seal ring. A first thermal interface material (TIM) is applied tothe seal ring. A lid is disposed over the seal ring. The first TIMthermally couples the lid to the seal ring. The first TIM fills the oneor more grooves after the lid is disposed over the seal ring.

In yet another embodiment, a method includes forming a seal ring on afirst side of a workpiece. The seal ring is etched to form at least onegroove in the seal ring. A first thermal interface material (TIM) isapplied to the seal ring. A second side of the workpiece is attached toa package carrier. The second side of the workpiece is opposite thefirst side of the workpiece. A lid is attached to the package carrierusing an adhesive. The lid extends along a sidewall of the workpiece andover the seal ring. The first TIM thermally couples the lid to the sealring. The first TIM fills the at least one groove after the lid isattached to the package carrier.

Although embodiments of the present disclosure and their advantages havebeen described in detail, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the disclosure as defined by the appendedclaims. For example, it will be readily understood by those of ordinaryskill in the art that many of the features, functions, processes, andmaterials described herein may be varied while remaining within thescope of the present disclosure. Moreover, the scope of the presentapplication is not intended to be limited to the particular embodimentsof the process, machine, manufacture, and composition of matter, means,methods or steps described in the specification. As one of ordinaryskill in the art will readily appreciate from the disclosure of thepresent disclosure, processes, machines, manufacture, compositions ofmatter, means, methods, or steps, presently existing or later to bedeveloped, that perform substantially the same function or achievesubstantially the same result as the corresponding embodiments describedherein may be utilized according to the present disclosure. Accordingly,the appended claims are intended to include within their scope suchprocesses, machines, manufacture, compositions of matter, means,methods, or steps.

What is claimed is:
 1. A method comprising: forming a seal ring on afirst side of a workpiece, wherein forming the seal ring on the firstside of the workpiece comprises: forming a dielectric layer over asubstrate of the workpiece; forming a recess in the dielectric layer;and filling the recess with a conductive material to form the seal ringwithin the dielectric layer; forming at least one groove in the sealring; applying a first thermal interface material (TIM) to the sealring; and attaching a lid over the workpiece, a first side of the lidhaving a recess, the lid covering the workpiece with the workpieceextending into the recess, a surface of the recess contacting the firstTIM, the first TIM extending into the at least one groove afterattaching the lid over the workpiece.
 2. The method of claim 1, furthercomprising: mounting a die over the first side of the workpiece, the diebeing in signal communication with the workpiece after mounting the dieover the first side of the workpiece; applying a first underfill betweenthe die and the workpiece; and applying a second TIM to the die, thesurface of the recess in the lid contacting the second TIM afterattaching the lid over the workpiece.
 3. The method of claim 2, furthercomprising: mounting the workpiece to a package carrier; applying asecond underfill between the workpiece and the package carrier; andapplying an adhesive to the package carrier, wherein attaching the lidover the workpiece comprises attaching the lid to the adhesive, andwherein the first TIM is disposed between the first underfill and thesecond underfill on the first side of the workpiece.
 4. The method ofclaim 3, wherein the first underfill extends along a first sidewall ofthe first TIM and the second underfill extends along a second sidewallof the first TIM, the first sidewall of the first TIM being opposite thesecond sidewall of the first TIM.
 5. The method of claim 1, furthercomprising forming at least one ridge on the first side of the lid,wherein attaching the lid over the workpiece comprises aligning the atleast one ridge with respect to the at least one groove.
 6. The methodof claim 1, wherein forming the at least one groove in the seal ringcomprises patterning the seal ring to form the at least one groove inthe seal ring.
 7. A method comprising: forming a dielectric layer over asubstrate; forming a recess in the dielectric layer; filling the recesswith a conductive material to form a seal ring within the dielectriclayer; patterning the seal ring to form one or more grooves in the sealring; applying a first thermal interface material (TIM) to the sealring; and disposing a lid over the seal ring, the first TIM thermallycoupling the lid to the seal ring, wherein the first TIM fills the oneor more grooves after disposing the lid over the seal ring.
 8. Themethod of claim 7, further comprising forming one or more ridges on afirst side of the lid, wherein the first TIM extends along sidewalls ofthe one or more ridges after disposing the lid over the seal ring. 9.The method of claim 8, further comprising aligning each of the one ormore ridges to a respective one of the one or more grooves.
 10. Themethod of claim 8, wherein a number of the one or more ridges is equalto a number of the one or more grooves.
 11. The method of claim 7,further comprising: attaching the substrate to a package carrier; andforming a first underfill between the substrate and the package carrier,the first underfill extending along a sidewall of the substrate.
 12. Themethod of claim 11, wherein disposing the lid over the seal ringcomprises attaching the lid to the package carrier using an adhesive.13. The method of claim 11, further comprising: attaching a die to thesubstrate, the substrate being interposed between the die and thepackage carrier; forming a second underfill between the die and thesubstrate; and applying a second TIM to the die, the second TIMthermally coupling the lid to the die.
 14. A method comprising: forminga seal ring on a first side of a workpiece, wherein forming the sealring on the first side of the workpiece comprises: forming a dielectriclayer over a substrate of the workpiece; patterning the dielectric layerto form a recess; and depositing a conductive material in the recess toform the seal ring within the dielectric layer; etching the seal ring toform at least one groove in the seal ring; applying a first thermalinterface material (TIM) to the seal ring; attaching a second side ofthe workpiece to a package carrier, the second side of the workpiecebeing opposite the first side of the workpiece; and attaching a lid tothe package carrier using an adhesive, the lid extending along asidewall of the workpiece and over the seal ring, the first TIMthermally coupling the lid to the seal ring, wherein the first TIM fillsthe at least one groove after attaching the lid to the package carrier.15. The method of claim 14, further comprising: attaching a die to thefirst side of the workpiece, the die being electrically coupled to theworkpiece; and depositing a second TIM over the die, the second TIMthermally coupling the die to the lid.
 16. The method of claim 15,further comprising forming a first underfill between the die and theworkpiece.
 17. The method of claim 16, further comprising forming asecond underfill between the workpiece and the package carrier.
 18. Themethod of claim 17, wherein the first underfill extends along a firstsidewall of the first TIM and the second underfill extends along asecond sidewall of the first TIM, the first sidewall of the first TIMbeing opposite the second sidewall of the first TIM.
 19. The method ofclaim 1, wherein the first TIM has a thermal conductivity between about0.5 W/(m·K) and about 10 W/(m·K).
 20. The method of claim 14, whereinthe at least one groove has a width between about 2 μm and about 30 μmand a depth between about 1 μm and about 50 μm.